In xe2x80x9csighting inxe2x80x9d firearms, such as rifles, shotguns, handguns, muzzle loaders, machine guns and cannons, for example, it is necessary to adjust the sights of the firearm at a pre-established angle with the bore of the barrel of the firearm, where the angle is determined by the distance from the muzzle of the firearm to the target, and by the trajectory of the bullet or projectile fired by the firearm. In its most basic form, this has been accomplished by mounting the firearm on a fixed stand or in a fixed position relative to a xe2x80x9csighting inxe2x80x9d target. In the past, the target was placed at the actual, final desired distance from the firearm; and a test shot was fired. The point on the target where the bullet or projectile entered the target then was aligned with the sight (whether iron sights or a telescope sight). After this was done, a second shot was fired; and the procedure was repeated until the point of entry of the bullet or projectile aligned with the cross hairs or cross points of the sights. In many cases, a number of shots needed to be fired in order to effect the sighting in procedure.
For each different range or target distance, a separate sighting in procedure needed to be followed. Obviously, a significant amount of ammunition needed to be expended simply to sight in the firearm; and the sighting in needed to be effected in a place where the firing of the actual bullet or projectile from the firearm over the desired distance could be effected safely. The result was a relatively time consuming, costly and potentially dangerous sighting in technique.
U.S. Pat. No. 4,825,258 is directed to a device for sighting in rifles and similar firearms without requiring the expenditure of several rounds of ammunition to effect the sighting in operation. The apparatus of this patent consists of a mounting assembly formed on a body of revolution and having a head portion, a mandrel portion, and a cylinder portion including an expansion tube or expandable arbor. The expandable arbor is inserted into the muzzle of the gun bore and is secured in an axial position; so that it aligns with the central axis of the gun bore. Manipulation of the device is necessary in order to effect the expansion of the arbor; and precautions must be taken not to mar the internal finish of the barrel into which the device is inserted. A light spot generator is mounted in axial alignment with the mounting assembly head portion and the mandrel; so that a light beam projected to a distant target provides a sighting reference for an associated scope or mechanical sight on the rifle. The expandable arbor and the complexity of this device limit its accuracy.
Another type of bore sighter has a mandrel or arbor which is inserted into the muzzle end of the bore of the rifle. A bore sighter with grid lines on it is mounted in an offset position on the arbor, in alignment with the scope or sight of the rifle. Once all of these parts have been secured together, the rifle is placed on a suitable fixed support; and the reticle of the telescopic sights of the rifle are aligned with the cross hairs of a graduated reticle in the bore sighter. The particular alignment is made in accordance with the indication on the grid for the desired range. Once this has been done, sighting in by means of the firing and adjusting of live ammunition is effected to make the final adjustments. Once the final adjustments have been made, the bore sighter once again is mounted on the rifle by inserting the arbor or mandrel into the end of the muzzle; and the recorded reticle position, where the cross hairs of the telescopic sight are in line with the graduated grid reticle in the bore sighter, is made for future reference. Using the scope adjustments, correction for bullet drop at a specific distance, provided the trajectory of a specific load is known, can be made. Each graduation on the bore sighter grid is equivalent to a particular drop at 100 yards. Consequently, when the scope reticle is below the grid center, the gun will shoot high to compensate for the drop or trajectory of the load. This is a relatively cumbersome device to use and requires the firing of live ammunition in its use.
Some types of sighting devices employ a laser beam or light beam mounted on the firearm sights; so that the beam indicates the alignment of the sights vis a vis the target. United States patents directed to this technique are the patents to Vogel U.S. Pat. No. 5,031,349; Idan U.S. Pat. No. 4,665,622; Snyder U.S. Pat. No. 4,295,289; and Snyder U.S. Pat. No. 4,079,534.
Other techniques have been employed for projecting a light through the gun barrel or firearm bore. The light is directed toward a target and is viewed through the firearm sight. Azimuth and elevation adjustments then are made in order to bring the projected light and the sight adjustments into proper alignment. A relatively complex device for accomplishing this purpose is described in the Cameron U.S. Pat. No. 5,060,391. This device employs an optical assembly, a beam splitter and an illumination source in an enclosure. The illumination source is used to provide a visible light which is directed by the beam splitter into the firearm bore, which is illuminated from the muzzle to the chamber. This illumination is viewed through the firearm optical sight; and the proper adjustments are made to bring the images of the muzzle and chamber into coincident alignment. When this accomplished, the cross hair of the firearm optical sight is adjusted to bring the cross hair into the alignment with the muzzle, bore and chamber images.
Another Edwards, U.S. Pat. No. 3,734,627, discloses an apparatus for aligning aircraft guns using a laser. The laser is mounted in a gun barrel; and the laser beam is used to locate a reference point for determining the adjustments needed in aligning the gun with respect to the gun sight. The device of this patent is not readily adaptable to hand-held firearms of various calibers.
Langner U.S. Pat. No. 5,454,168 also is directed to an apparatus for bore sighting hand-held firearms. The apparatus of this patent includes a light source contained within a housing placed in the firing chamber of the firearm. Light is projected from the housing through the bore of the barrel and through the muzzle to a target placed at a pre-established distance from the muzzle. Calibrated points are marked on the target; and the sights of the firearm are adjusted to the calibrated points to effect the bore sighting of the firearm for a specific range. The bore sighting apparatus of this patent includes a housing in the form of a stepped cylindrical section for utilization with different calibers of firearms; but a wide range of different calibers or different types of firearms cannot be employed with a single device.
Another Lanning U.S. Pat. No. 4,481,561 uses a flashlight for bore sighting with a long barreled shotgun or rifle. The flashlight itself includes a cartridge case, with an ejector, rim and primer opening in the base, and a side wall defining an open front end. The battery and light bulb are located within the case; and a switch pin is placed in the primer opening to complete the circuit for illuminating the bulb. When the breach of the gun is closed, a spring coupled with the switch pin is moved to energize the lightbulb.
It is desirable to provide a simple bore sighting device which provides accurate bore sighting, which is capable of utilization with a range of firearms of different types and different calibers, which quickly and effectively facilitates the bore sighting adjustments of the sights of the firearm, and which is easy to use.
It is an object of this invention to provide an improved bore sighter for a firearm.
It is another object of this invention to provide an improved, easy-to-use bore sighting apparatus for use with firearms of different calibers.
It is an additional object of this invention to provide an improved bore sighting apparatus inserted into the muzzle of a firearm.
It is a further object of this invention to provide an improved bore sighting apparatus inserted into the muzzle of a firearm and held in place during the bore sighting operation by means of magnetic force.
In accordance with a preferred embodiment of this invention, a bore sighting apparatus includes a housing having first and second ends and containing a light source for projecting a beam of light from the first end of the housing. A down-tapered portion extends from the second end of the housing for engaging the muzzle of a firearm. This down-tapered portion includes an extension which fits into the interior of the barrel of a firearm; and a magnet is located in the down-tapered portion to assist in holding the housing in place on the end of the barrel of a firearm when it is in use.